In Portuguese, why would positive belief be an indicative form, but negative belief be subjunctive?

Question

From what I understand, the indicative mood is for actions/events that are generally regarded as factual or certain, and the subjunctive mood is for actions or events that may or may not be true, uncertainty, and wanting, requesting something from anything or anyone other than yourself.

However when it comes to beliefs, I'm totally confused by the reasoning. Why would a positive belief be indicative when the belief may be right or wrong? Is there a logical explanation?

Answer 1

let me see....

acho que ele é
não acho que ele seja

acho que ela entende
não acho que entenda

acho que ele disse isso
não acho que ele tenha dito isso

I think it's correct... the positive belief takes indicative form, and negative subjunctive, at least most of the time. I have never realised that, but I do follow this pattern in my speech.

I don't think there is much logic to it, but the form becomes fixed with repetition.

Answer 2

Excuse but I didn't understand your question. You should have given examples.